The central goal of this project is to try to elucidate the biochemical basis of the regulation of HIV mRNA 3' processing. The long-term objective is to exploit the unique nature of the HIV poly(A) site processing signal to design an effective antiviral agent. The investigator proposes to identify the factor responsible for recognition of the HIV poly(A) site upstream element and the mechanism by which it enhances processing will be delineated.The subsequent cloning of this upstream factor and the characterization of its functional domains will permit the alteration of the RNA-binding specificity of the factor in order to facilitate recognition and subsequent processing of the HIV 5' core poly(A) site. A well-characterized in vitro processing system will be employed to probe the biochemical basis of the regulation of HIV mRNA 3' end formation. The investigator has five specific aims the first of which is to try to identify the processing factor that interacts with the HIV poly(A) site upstream element. Next, the author proposes to elucidate the mechanism by which the upstream factor functions to enhance processing at the HIV poly(A) site. Third, he will attempt to purify biochemically the HIV poly(A) site upstream factor and to isolate the corresponding cDNA clones. He also proposes to identify the domains of the upstream factor that mediate sequence recognition and function to enhance processing. Lastly, the author will try to develop a chimeric processing factor, and potential antiviral agent, to facilitate processing at the HIV 5' core poly(A) site.